These are actually wild (or feral) river plums, where the trees grow on the banks of the river and the vast majority of the crop would either only be accessible by boat, or else drops from on high (the trees are about 20 feet tall) and rolls straight down the banks into the water anyway :-D

But I think you're right and the locals have cottoned onto the foraging possibilities... I was just surprised that there wasn't more inaccessible (almost all of it) or unripe fruit visible up on the trees, even if there wasn't much on the path underneath them.